their extinction. If it is not known when it ends, such as if he endows it upon a group whose extinction is permitted by custom, and he did not designate its end for the needy, nor for an unending category, the endowment is valid. This is the opinion of Malik, Abu Yusuf, and al-Shafi'i in one of his two narrations. Muhammad ibn al-Hasan said: It is not valid. This is the second opinion of al-Shafi'i, because the implication of an endowment is perpetuity, so if it is terminable, it becomes an endowment upon an unknown, thus it is invalid, just as if he had endowed it upon an unknown entity at the beginning. Our argument is that it is an act of disposition whose beneficiary is known, so it is valid, just as if he had explicitly stated its continuous beneficiary. Furthermore, because when an absolute expression has a [customary] usage, it is interpreted according to it, like the currency of the land and the custom regarding the beneficiary; here, they are the most deserving of categories for it, so it is as if he had specified them. Once this is established, then upon the extinction of those for whom it was endowed, it reverts to the relatives of the endower (2). This is also the position of al-Shafi'i. There is another narration from Ahmad that it reverts to the needy. This was chosen by al-Qadi and al-Sharif Abu Ja'far, because they (3) are the beneficiaries of alms and the rights of God Almighty such as expiations and the like. Therefore, if there is a charity for which no specific beneficiary is determined, it reverts to them, just as if one vowed an absolute charity. There is a third narration from Ahmad that it is placed in the public treasury (Bayt al-Mal) of the Muslims, because it is wealth that has no one entitled to it, so it resembles the wealth of one who has no heir. Abu Yusuf said: It reverts to the endower and his heirs (4), unless he says: "It is an endowed charity, from which sustenance is provided to so-and-so and so-and-so." If the named person becomes extinct, it belongs to the poor and needy, because he made it a charity for a named person, so it cannot be for anyone else. It differs from the case where he says: "Sustenance is provided from it to so-and-so and so-and-so," for he has made the charity absolute. Our argument is that he has removed his ownership for the sake of God Almighty, so it is not permissible for it to revert to him, just as if he had freed a slave. The evidence for distributing it to the relatives of the endower is that they are the most deserving of people of his charity, based on the saying of the Prophet (peace and blessings be upon him): "Your charity to other than your kin is charity, and your charity to your kin is both charity and maintaining kinship ties" (5). He also said: "For you to leave your heirs wealthy is better than that...